What are Intrusion Detection Systems?

Intrusion Detection System (IDS) are a necessary part of any strategy for enterprise security. What are Intrusion Detection systems? CERIAS, The Center for Education and Research in Information Assurance and Security, defines it this way:


“The purpose of an intrusion detection system (or IDS) is to detect unauthorized access or misuse of a computer system. Intrusion detection systems are kind of like burglar alarms for computers. They sound alarms and sometimes even take corrective action when an intruder or abuser is detected. Many different intrusion detection systems have been developed but the detection schemes generally fall into one of two categories, anomaly detection or misuse detection. Anomaly detectors look for behavior that deviates from normal system use. Misuse detectors look for behavior that matches a known attack scenario. A great deal of time and effort has been invested in intrusion detection, and this list provides links to many sites that discuss some of these efforts”(http://www.cerias.purdue.edu/about/history/coast_resources/intrusion_detection/)

There is a sub-category of intrusion detection systems called network intrusion detection systems (NIDS). These systems monitors packets on the network wire and looks for suspicious activity. Network intrusion detection systems can monitor many computers at a time over a network, while other intrusion detection systems may monitor only one.
Who is breaking into your system?


One common misconception of software hackers is that it is usually people outside your network who break into your systems and cause mayhem. The reality, especially for corporate workers, is that insiders can and usually do cause the majority of security breaches. Insiders often impersonate people with more privileges then themselves to gain access to sensitive information.
How do intruders break into your system?


The simplest and easiest way to break in is to let someone have physical access to a system. Despite the best of efforts, it is often impossible to stop someone once they have physical access to a machine. Also, if someone has an account on a system already, at a low permission level, another way to break in is to use tricks of the trade to be granted higher-level privileges through holes in your system. Finally, there are many ways to gain access to systems even if one is working remotely. Remote intrusion techniques have become harder and more complex to fight.
How does one stop intrusions?


There are several Freeware/shareware Intrusion Detection Systems as well as commercial intrusion detection systems.


Open Source Intrusion Detection Systems


Below are a few of the open source intrusion detection systems:


AIDE (http://sourceforge.net/projects/aide) Self-described as “AIDE (Advanced Intrusion Detection Environment) is a free replacement for Tripwire. It does the same things as the semi-free Tripwire and more. There are other free replacements available so why build a new one? All the other replacements do not achieve the level of Tripwire. And I wanted a program that would exceed the limitations of Tripwire.”


File System Saint (http://sourceforge.net/projects/fss) – Self-described as, “File System Saint is a lightweight host-based intrusion detection system with primary focus on speed and ease of use.”


Snort (www.snort.org) Self-described as “Snort® is an open source network intrusion prevention and detection system utilizing a rule-driven language, which combines the benefits of signature, protocol and anomaly based inspection methods. With millions of downloads to date, Snort is the most widely deployed intrusion detection and prevention technology worldwide and has become the de facto standard for the industry.”
Commercial Intrusion Detection Systems

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Courtesy:http://xtreme8.wordpress.com/2008/06/12/what-are-intrusion-detection-systems/

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IPS: Next generation IDS

An IPS offers the ability to identify an intrusion, relevance, impact, direction and proper analysis of an event and then pass the appropriate information and commands to the firewalls, switches and other network devices to mitigate the event’s risk.
The key technical components of IPS include the marriage of global and local host controls, IDS, global and local security policy, risk management software and globally accessible consoles for managing IPS.


An IPS is the next security layer to be introduced that combines the protection of firewall with the monitoring ability of an IDS to protect our networ with the analysis necessary to make the proper decision on the fly.



IDS started the overall protection by first protecting host(HIDS), then network (NIDS). First and second generation IDS currently protects our network by identifying the threats. IDS provides real time alerts and reports. They cannot provide the necessary intelligence to notify all the network components downstream and upstream from the point of identification. This is where the IPS becomes the part of overall layered approach to security. IPS gathers all network information and make determination of the threat, then notify all other devices of those findings. Upstream providers can notify the downstream customers of possible attacks before or during the events as that malicious attempts arrives and vice versa.
Although IPS are actually the next generaton IDS, there will always be a need to keep those seperate technologies. Security devices must remain seperate to allow depth in overall protection; thus , firewall will need IDS and the network will need IPS. Each techology is bound to each other with the dependencies that will not disappear.


IPS has all the features of a good IDS, but can also stop malacious traffic from invading the enterprise. Unlike an IDS, an IPS sits inline with traffic flow on a network, actively shutting down attempted attacks as they are sent over the wire. It can stop the attack by terminating the network connection or user session originating the attack, by blocking access to traget from the user account, IP address or other attributes assocaited with that attacker, or by blocking all access to the targetted host, services, or application.

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Courtesy:http://technocache.wordpress.com/2009/03/02/ips-next-generation-ids/

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